Disclosure: I work at Google. You can consider looking at Glassdoor[1], bearing in mind this includes data from several years ago before the wage-fixing bust and excluding natural growth. Looking at offers that I have friends have gotten at both bigtech and not, a good rule of thumb for new offers is to take the upper end of what Glassdoor says and add ~10%. If you want you can also look at H-1B data[2] which usually quotes only guaranteed base salary (and excludes bonus and RSUs). As far as I know there is no public data on this.

[1] - https://www.glassdoor.com/Salary/Google-Software-Engineer-II... [2] - http://h1bdata.info/index.php?em=google&job=software+enginee...